Position switches are widely used today to detect and report the position of various mechanical components or devices. For example, many actuators use position switches to detect and report when an actuated part reaches an end or some other discrete position along a defined range of motion. In some cases, a controller receives a signal from a position switch, and uses that signal to cut power to the actuator when the end or other position is reached.
In some cases, one or more position switches may be used to help control other components within a system. For example, FIG. 1 is a schematic diagram of an example system that uses two position switches to help control other components within the system. FIG. 1 includes an actuator 10, a controller 12, a motor 14, a gear train 16, two mechanical position switches 18a and 18b, and an actuated part 20. The controller 12 controls the operation of the motor 14, and the motor 14 moves the position of the actuated part 20 via the gear train 16.
Each of the mechanical position switches 18a and 18b detect and report when the actuated part 20 reaches some discrete position along a defined range of motion. Each of the mechanical position switches 18a and 18b is shown having a lever 22a and 22b, respectively, that slide along a drive shaft 26 that extends between the gear train 16 and the actuated part 20. The drive shaft 26 shown in FIG. 1 has two cams 24a and 24b. The cams 24a and 24b are shown fixed relative to the drive shaft 26, and thus turn with the drive shaft 26. The cams 24a and 24b project laterally away from the shaft 26 at discrete locations such that when the drive shaft 26 is rotated, the cams 24a and 24b push the corresponding lever 22a and 22b away from the shaft 26 at corresponding discrete shaft positions. For example, and in FIG. 1, cam 24a is shown pushing lever 22a away from the drive shaft 26, thereby causing the mechanical position switch 18a to close, while cam 22b is shown as not pushing lever 22b away from the drive shaft 26, thereby allowing the mechanical position switch 18b to remain open. The drive shaft position shown in FIG. 1 may correspond to one defined end position of the actuated part 20. When the motor 14 rotates the drive shaft 26 to another end position, the cam 22b may push lever 22b away from the drive shaft 26, thereby causing the mechanical position switch 18b to close, while cam 22a may then not push lever 22a away from the drive shaft 26, thereby causing the mechanical position switch 18a to be open. As can be seen, the cams 24a and 24b, levers 22a and 22b and mechanical switches 18a and 18b may be used to detect when the actuated part 20 reaches two discrete positions along a defined range of motion. In some cases, more or less cams, levers and mechanical switches may be provided to detect other defined discrete positions of the actuated part 20.
The mechanical position switches 18a and 18b may be electrically coupled to one or more control signals 28a and 28b that can be used to help control (e.g. enable or disable) one or more other components (not shown) of a system. In some cases, the control signals 28a and 28b may be higher voltage signals, and care must be taken to use appropriately rated mechanical position switches 18a and 18b. Also, care must be taken to adhere to appropriate regulatory standards (such as the UL standard) dealing with higher voltage lines.
Many actuators with such mechanical position switches, levers and cams do not lend themselves very well to automated assembly. Moreover, reconfiguring such actuators in the field can be time consuming and tedious. For example, to change the switch settings of such an actuator, the cams 24a and 24b and/or the one or more levers 22a and 22b may have to be manually moved and positioned to properly set the desired switch points along the range of motion of the actuated part 20. In addition, and in some cases, the operating cams 22 and levers 24 can be susceptible to mechanical wear, which can result in decreased accuracy, and in some cases, reduced reliability and even failure. Furthermore, when the control signals 28a and 28b are higher voltage signals, the design of the actuator can become complicated because running and routing high voltage wires and/or traces in such a way to satisfy UL or other standards can be challenging.